Polythialkylenediols as sensitizers for photographic silver halide emulsions



United States Patent 3,021,215 POLYTHIAALKYLENEDIOLS AS SENSITIZERS FOR PHOTOGRAPHIC SERVER HALIDE EMULSIONS Jack L. R. Williams and Bernard C. Cossar, Rochester,

N.Y., assignors to Eastman Kodak Company, Rochester, N.Y., a corporation of New Jersey No Drawing. Filed Oct. 1, 1959, Ser. No. 843,638 18 Claims. (Cl. 96-100) This invention relates to photographic silver halide emulsions, and more particularly, to an improved means for sensitizing such photographic silver halide emulsions. A number of methods have been previously described for increasing the sensitivity of photographic silver halide emulsions, other than methods of optical or spectral sensitization which involve the incorporation of certain colored compounds or dyes in the emulsions. The incorporation of such dyes in the emulsions increases the optical range of sensitivity, and for this reason such dyes are commonly referred to as optical or spectral sensitizing dyes. It is also well known to increase the sensitivity of photographic emulsions by addition of sulfur compounds capable of reacting with silver salts to form silver sulfide, or with reducing agents (compounds of these types are also naturally present in gelatin), or with salts of gold or other noble metals, or with combinations of two or more of the aforementioned compounds generally known as chemical sensitizers. Such chemical sensitizers are believed to react with the silver halide to form, on the surface of the silver halide, minute amounts of silver sulfide or of silver or of other noble metals, and these processes are capable of increasing the sensitivity of developing-out emulsions by very large factors. The process of chemical sensitization, however, reaches a definite limit beyond which further addition of sensitizer, or of further digestion with the sensitizer present, merely increases the fog of the photographic emulsion with constant or decreasing speed.

We have now found a means of further increasing the sensitivity of photographic emulsions which may be applied even though the ordinary processes of chemical sensitization have been carried to the eflfective limit of the photographic emulsion in question. Our process is to be distinguished from hypersensitization, which is produced by bathing a finished coating with solutions of ammonia, amines or silver salts. Such processes act primarily on optically sensitized photographic emulsions and tend to increase the free silver ion concentration of the emulsion and greatly diminish its stability. Our process is also to be distinguished from hypersensitization by mercury vapor, which gives a transitory effect which is lost on storage of the film. The compounds used in our invention do not appear to be chemical sensitizers in the usual sense, since they increase speed by their presence during exposure and processing and require no digestion with the photographic emulsion to produce an increase in speed, nor does their chemistry indicate that they are likely to react with silver halide under normal emulsion conditions.

The novel sensitizers of our invention are quite unique in that the effects produced are additive in photographic emulsions which have already been sensitized to their optimum, or near-optimum, with conventional chemical sensitizers, such as labile sulfur compounds. The novel sensitizers of our invention, however, can be used to sensitize photographic silver halide emulsions containing no other sensitizers, if desired. The novel sensitizers of our invention are not strictly chemical sensitizers, since chemical sensitizers do not generally provide the additive effects of the type mentioned.

It is, therefore, an object of our invention to provide 3,021,215 Patented Feb. 13, 1962 ice containing labile sulfur atoms, or gold-containing com-' pounds. Other objects will become apparent from a consideration of the following description and examples.

According to our invention, we have found that the sensitivity of an ordinary photographic silver halide-emulsion can be materially increased by incorporating therein nonpolymeric compounds which can be characterized as polythia-alkylenediols. These non-polymeric compounds contain their sulfur atoms in the form of thioether linkages. By thioether linkages, we mean a linkage wherein the sulfur atom is a divalent atom joined to two nonoxocarbonylic carbon atoms. Compounds useful in sensitizing photographic silver halide emulsions according to our invention are to be distinguished from the polymeric thioether compounds described in US. application Serial No. 779,874, filed December 12, 1958, by J. R Dann and J. J. Chechak. The polymeric compounds described in this latter application are generally characterized as having a relatively high molecular weight and containing characteristic repeating groups.

The sensitizing compounds useful in practicing our invention include compounds represented by the followi ing general formula: (I) HOR(SR S-ROH wherein R and R each represents an alkylene group, such as ethylene, trimethylene, tetramethylene (butylene), methyl-substituted trimethylene, pentamethylene, ethyl substituted tetramethylene, hexamethylene, heptamethylene, octamethylene, nonamethylene, decamethylene, etc.-

(Ia) HO-(CH fiS-(CH ),,$--(CH OH wherein m and n each represents a positive integer of from about 2 to 10.

The compounds of Formulas I and Ia above can be prepared according to methods which have been previously described in the prior art. For example, these compounds can be prepared by condensing a dihalogenated compound together with an alkali metal salt of a mercaptoalkanol. Alternatively, these sensitizing compounds can be prepared by condensing an alkylene chlorohydrin with an alkali metal salt of an alkanedithiol. Still another method for preparing the higher alkylene derivatives is by reaction of a diene with a mercapto alcohol. These three alternative methods of syntheses can be outlined as follows:

Method A: Reaction of an alkylene dihalide with a mercapto alcohol 2)6 2)5 2)6 Method B: Reaction of an alkylene chlorohydrin with a dithiol NaS (CH SNa+2Cl CH 0H 2)6 2)5 2)6 Method C: Reaction of a diene with a mercapto alcohol Another object of EXAMPLE 3 v M ethod C.7,13-dithianonadecan-l ,1 9-di0l A mixture of 13.6 g. (0.2 mole) of 1,4-pentadiene and 5 5 3.6 g. (0.4 moles) of 6-mercapto-1-hexanol was irradiated for 1.5 hours at a distance of ten inches from a 360- watt mercury lamp. The reaction mixture was dissolved in ether and the solution cooled in a Dry Ice acetone bath to give, after filtration and drying, g. (28 percent of Analysis.Calcd. for C H S O C, 59.9; H, 10.4; S, 19.6. Found: C, 60.0; H, 10.7; S, 19.7.

In the following table are given the analyses and melting point (where available) for a number of compounds 5 prepared according to one of the three methods illustrated in Examples 1, 2 and 3 above. In the table, an asterisk means that the product obtained was not a crystalline, solid at normal room temperature.

Analyses ing ex- The TABLE I m 5 e amel l mw snm n scene nwmnmmne m ueaimmunnuuwnnemm -mnnw mnnnmmmn u s9,9.,,,.s1,L..,9,9,.L,,-6.11", HUWHHHHHHHYHIHHHHHHWWIHHH IHIHHHHH "H in the follow EXAMPLE 1 To the cooled reaction mixture Formula y 0 000000 00000000 0000 0000000000 Zflfl. fimfitflfififivvm fi Z2 00 OOOOOOOOOOOOOOOO 2 OOO QSOOSOOOOO 0O 22 i zaiiiz aizzzzi sizz 2 22 22222 as we eseeeeeeseesteesieeashes. eme tweeeee. .Z. if.........f....fi. .3-.. 11-3.3.3... r {T1 3 1 1.1 ii 1 1 .I I I d mm mm 0m 00 00000000000000000 0000 0000000000 P Tr YTTPYTFF.TYTYPYYYTY.T.Y r.ffr.f frrr. mm .mm memmmmmmmmmmmmnmm mmmm "mmmmmmmmmm a an a a a ll 11 aa aa a CC CC "C 'lhese methods are illustrated amples:

j To a cold solution of 11.5 g. 0.5 g. atom) of sodium in 500 ml. of methanol there were added 67 g. (0.5 mole) Analysis.Calcd. for C17H35S2O2Z S,- 19.6. Found: C, 59.6;1-1, 10.8; S, 19.6.

there were added with stirring 57 g. (0.25 mole) of 1,5 dibromopentane. The reaction mixture was allowed to 10 theory) of solid, MP. 67 C. remain at room temperature overnight, after which time the methanol was removed at reduced pressure.

residue was mixed with one liter of Water and the whole extracted with chloroform. The chloroform was distilled and the residue recrystallized from acetone to give 62 g. 1 (70 percent of theory) of the dithiadiol, MP. 67.5 C.

Gom-

pound Method 0. 0000 -0000 0 0000 00000000 0 :C .220 .d. n d dddd.. dddd on ddd d ddddd d md nmmmd nmmn umnnn n nmnm nnnmn .mmmu mur unm uuuu huuuruuu .u 0 000GB OOOOH OFOOOO 000G0000C0 FommFFFFoMFFFF MF FFFF FFFFFFFF F F F b w n a sl ssaa u 41 54.5AO9547.0.318.4.32 .6 3 2 2035 2 1 %2 11wm %2111% 2 1112 1lll1211 M1. SSSSSSSS S A. 5 ..4.A.46

- In a manner similar to that illustrated, other non-pol meric sensitizers embraced by Formula I above can be V, prepared. Those sensitizers containing 3 or 4 sulfur 0 m 5011x1011 0f 8- atOm) Sodium 5 atoms can be prepared by using reactants which contain in 500 ml. of methanol, there were added with cooling 68 1,19-nonadecanediol was prepared by method B above by replacing the disodium salt with a molecularly equivalent By use 70 amount of the disodium. salt of B-thiapentane-l,S-dithiol. of the isolation procedure used in Example 1, there was The sensitizing compounds of our invention can be added to ordinary photographic silver halide emulsions for the purpose of increasing the sensitivity thereof, as has been indicated above.

one or two sulfur atoms between the functional groups at either end of the molecule. For example, 7,10,13-trithiae second reactant was, of course, 6-chloro-n-hexanol.

1 Not crystalline solids at room temperature. 1 Liquid. 3 1.5 mm.

EXAMPLE 2 Method B.-7,13-dithian0nadecan-l ,19-a'i0l AnUlySiS--CaiCd. for C1|1H3S202Z C. H, S, 19.6. Found: C, 59.6; H, 10.8; S, 19.6.

g. (0.5 mole) of 1,5-pentanedithiol. After the addition of 136.5 g. (1.0 mole) of hexamethylene chlorohydrin with cooling and stirring, the reaction mixture was allowed to remain at room temperature overnight.

obtained g. (72 percent of theory) of the dithiadiol, M.P. 67.5 C.

The preparation of photographic silver halide emulsions involves three separate operations: (1) emulsification and digestion of silver halide, (2) the freeing of the emulsion of excess water-soluble salts, usually by washing With water, and (3) the second digestion or afterripening to obtain increased emulsion speed or sensitivity. (Mees, The Theory of the Photographic Process, 1954.) The sensitizers of our invention can be added to the emulsion before the final digestion or after-ripening, or they can be added immediately prior to the coating. Our new photographic sensitizers require no special final digestion or after-ripening.

The particular quantity of sensitizer used in a given emulsion can vary, depending upon the eiiects desired, degree of ripening, silver content of the emulsion, etc. The amount used is also dependent upon the particular stage at which the sensitizer was added during the preparation of the emulsion. We have found that generally from about 50 mg. to about 5 g. of sensitizer per mole of silver halide are quite adequate to accomplish the desired sensitization.

The sensitizers of our invention can be added to photographic emulsions using any of the well-known techniques in emulsion making. For example, the sensitizers can be dissolved in a suitable solvent and added to the silver halide emulsion, or they can be added to the emulsion in the form of a dispersion similar to the technique used to incorporate certain types of color-forming compounds (couplers) in a photographic emulsion. Techniques of this type are described in Jelley et al. U.S. Patent 2,322,027, issued June 15, 1943, and Fierke et a1. U.S. Patent 2,801,171, issued July 30, 1957. As indicated above, the solvent should be selected so that it has no harmful eifect upon the emulsion, and generally solvents or diluents which are miscible with water are to be preferred. Water or dilute alkali is a dispersing medium for some of the seusitizers of the invention. In a preferred embodiment, the sensitizer can be dissolved in a solvent, such as ethanol, acetone, pyridine, N,N-dimethylfor1n.- amide, etc., and added to the emulsion in this form. If desired, certain of the sensitizers can be prepared in finelydivided form and dispersed in water alone, or in the presence of a suitable dispersing agent (such as alkali metal salts of aromatic or aliphatic sulfonic acids) and added to the emulsion in this form. It is quite apparent that the sensitizers of our invention should have sufficient water-dispersibility so that they can be adsorbed to or associated with the grains of the silver halide present in the emulsion in sufiicient amount to sensitize the emulsion. It is apparent that the optimum amount for each of the sensitizers will vary somewhat from emulsion to emulsion and from compound to compound. The optimum amount of any given sensitizer can be determined for any particular emulsion by running a series of tests in which the quantity of sensitizer is varied over a given range. Exposure of the treated emulsion in conventional photographic testing apparatus, such as an intensity scale sensitometer, will reveal the most advantageous concentrations for that sensitizer in that particular emulsion. Sach matters are well understood by those skilled in the art.

The photographic emulsions used in practicing our invention are, of course, of the developing-out type.

The emulsions can be chemically sensitized by any of the accepted procedures. The emulsions can be digested with naturally active gelatin, or sulfur compounds can be added such as those described in Sheppard U.S. Patent 1,574,944, issued March 2, 1926; Sheppard et al. U.S. Patent 1,623,499, issued April 5, 1927, and Sheppard and Brigham U.S. Patent 2,410,689, issued November 5, 1946.

The emulsions can also be treated with salts of the noble metals such as ruthenium, rhodium, palladium, iridium, and platinum. Representative compounds are ammonium chloropalladate, potassium chloroplatinate, and

sodium chloropalladite, which are used for sensitizing in amounts below that which produces any substantial fog inhibition, as described in Smith and Trivelli U.S. Patent 2,448,060, issued August 31, 1948, and as anti-foggants in higher amounts, as described in Trivelli and Smith U.S. Patents 2,566,245, issued August 28, 1951, and 2,566,263, issued August 28, 1951.

The emulsions can also be chemically sensitized with gold salts as described in Waller et al. U.S. Patent 2,399,083, issued April 23, 1946, or stabilized with gold salts as described in Damschroder U.S. Patent 2,597,856, issued May 27, 1952, and Yutzy and Leermakers U.S. Patent 2,597,915, issued May 27, 1952. Suitable compounds are potassium chloroaurite, potassium aurithiocyanate, potassium chloroaurate, auric trichloride and 2-aurosulfobenzothiazole methochloiide.

The emulsions can also be chemically sensitized with reducing agents, such as stannous salts (Carroll U.S. Patent 2,487,850, issued November 15, 1949), polyamines, such as diethyltriamine (Lowe and Jones U.S. Patent 2,518,698, issued August 15, 1950), polyamines, such as spermine (Lowe and Allen U.S. Patent 2,521,925, issued September 12, 1950), or bis(fi-aminoethyl)sulfide and its water-soluble salts (Lowe and Jones U.S. Patent 2,521,926, issued September 12, 1950).

The emulsions can also be optically sensitized with cyanine and merocyanine dyes, such as those described in Brooker U.S. Patents 1,846,301, issued February 23, 1932; 1,846,302 issued February 23, 1932; and 1,942,854, issued January 9, 1934; White U.S. Patent 1,990,507, issued February 12, 1935; Brooker and White U.S. Patents 2,112,140, issued March 22, 1938; 2,165,338, issued July 11, 1939; 2,493,747, issued January 10, 1950 and 2,739,964, issued March 27, 1956; Brooker and Keyes U.S. Patent 2,493,748, issued January 10, 1950; Sprague U.S. Patents 2,503,776, issued April 11, 1950, and 2,519,001, issued August 15, 1960; Heseltine and Brooker U.S. Patent 2,666,761, issued January 19, 1954; Heseltine U.S. Patent 2,734,900, issued February 14, 1956; Van Lare U.S. Patent 2,739,149, issued March 20, 1956; and Kodak Limited British Patent 450,958, accepted July 15, 1936.

The emulsions can also be stabilized with the mercury compounds of Allen, Byers, and Murray U. S. Patent 2,728,663, issued December 27, 1955; Carroll and Mur- Y ray U.S. Patent 2,728,664, issued December 27, 1955'; and Leubner and Murray U.S. Patent 2,728,665, issued December 27, 1955; the triazoles of Heimbach and Kelly U.S. Patent 2,444,608, issued July 6, 1948; the azaindenes of Heimbach and Kelly U.S. Patents 2,444,605 and 2,444,606, issued July 6, 1948; Heimbach U.S. Patents 2,444,607, issued July 6, 1948, and 2,450,397, issued September 28, 1948; Heimbach and Clark U.S. Patent 2,444,609, issued July 6, 1948; Allen and Reynolds U.S. Patents 2,713,541, issued July 19, 1955, and 2,743,181, issued April 24, 1956; Carroll and Beach U.S. Patent 2,716,062, issued August 23, 1955; Allen and Beilfuss U.S. Patent 2,735,769, issued 'February 21, 1956; Reynolds and Sagal U.S. Patent 2,756,147, issued July 24, 1956; Allen and Sagura U.S. Patent 2,772,164, issued November 27, 1956, and those disclosed by Birr in Z. wiss. Phot., vol. 47, 1952, pages 2-28; the disulfides of Kodak Belgian Patent 569,317, issued July 31, 1958; the quaternary benzothiazolium compounds of Brooker and Stand U.S. Patent 2,131,038, issued September 27, 1938, or Allen and Wilson U.S. Patent 2,694,716, issued Nevember 16, 1954 (e.g., decamethylene-bis-benzothiazolium perchlorate); or the zinc and cadmium salts of Jones U.S. Patent 2,839,405, issued June 17, 1958; and the carboxymethylmercapto compounds of Murray, Reynolds and Van Allan U.S. Patent 2,819,965, issued January 14, 1958.

The emulsions may also contain speed-increasing compounds of the quaternary ammonium type of Carroll U.S. Patent 2,271,623, issued February 3, 1942; Carroll and Allen U.S. Patent 2,288,226, issued June 30, 1942 Carroll and Spence U.S. Patent 2,334,864, issued Novem tion Serial No. 779,839, filed December 12, 1958, or

Dann and Chechak U.S. application Serial No. 779,874, filed December 12, 1958.

The emulsions may contain a suitable gelatin plasticizer such as glycerin; a dihydroxy alkane such as 1,5- pentane diol as described in Milton and Murray U.S. application Serial No. 588,951, filed June 4, 1956, now U.S. Patent No. 2,960,404; an ester of an ethylene bisglycolic acid such as ethylene bis(methyl glycolate) as described in Milton U.S. application Serial No. 662,564, filed May 31, 1957, now U.S. Patent No. 2,904,343; bis- (ethoxy diethylene glycol) succiuate as described in Gray U.S. application Serial No. 604,333, tiled August 16, 1956, now U.S. Patent No. 2,940,854, or a polymeric hydrosol as results from the emulsion polymerization of a. mixture of an amide of an acid of the acrylic acid series, an acrylic acid ester and a styrene-type compound as described in Tong U.S. Patent 2,852,386, issued September 16, 195 8. The plasticizer may be added to the emulsion before or after the addition of a sensitizing dye, if used.

The emulsions may be hardened with any suitable hardener for gelatin such as formaldehyde; :1 halogen-substituted aliphatic acid such as mucobromic acid as described in White U.S. Patent 2,080,019, issued May 11, 1937; a compound having a plurality of acid anhydride groups such as 7,8-diphenylbicyclo(2,2,2)-7-octene-2,3,- 5,6-tetracarboxylic dianhydride, or a dicarboxylic or a disulfonic acid chloride such as terephthaloyl chloride or naphthalene-1,5-disu1fonyl chloride as described in Allen and Carroll U.S. Patents 2,725,294 and 2,725,295, both issued November 29, 1955; a cyclic 1,2-diketoue such as cyclopentane-l,2-dione as described in Allen and Byers U.S. Patent 2,725,305, issued November 29, 1955; a bisester of methane-sulfonic acid such as LZ-di-(methanesulfonoxy)-ethane as described in Allen and Laakso U.S. Patent 2,726,162, issued December 6, 1955; 1,3-dihydroxymethyl-benzimidazol-Z-one as described in July, Knott and Pollak U.S. Patent 2,732,316, issued January 24, 1956; a

dialdehyde or a sodium bisulfite derivative thereof, the aldehyde groups of which are separated by 2-3 carbon atoms, such as fl-methyl glutaraldehyde bis-sodium bisul- -fite as described in Allen and Burness U.S. patent application Serial No. 556,031, filed December 29, 1955, now abandoned; a bisaziridine carboxamide such as trimethylene bis(1-aziridine carboxamide) as described in Allen and Webster U.S. patent application Serial No. 599,891, filed July 25, 1956, now U.S. Patent No. 2,950,197; or 2,3-dihydroxy dioxane as described in Jeifreys U.S. Patent 2,870,013, issued January 20, 1959.

The emulsions may contain a coating aid such as saponin; a lauryl or oleoyl monoether of polyethylene glycol as described in Knox and Davis U.S. Patent 2,831,766, issued April 22, 1958; a salt of a sulfated and alkylated polyethylene glycol ether as described in Knox and Davis U.S. Patent 2,719,087, issued September 27, 1955; an acylated alkyl taurine such as the sodium salt of N-oleoyl- N-methyl taurine as described in Knox, Twardokus and Davis U.S. Patent 2,739,891, issued March 27, 1956; the reaction product of a dianhydride of tetracarboxybutane with an alcohol or an aliphatic amine containing from 8 to 18 carbon atoms which is treated with a base, for example, the sodium salt of the monoester of tetracarboxybutane as described in Knox, Stenberg and Wilson U.S. Patent 2,843,487, issued July 15, 1958; a water-soluble maleopimarate or a mixture of a water-soluble maleopimarate and a substituted glutamate salt as described in Knox and Fowler U.S. Patent 2,823,123, issued February 11, 1958; an alkali metal salt of a substituted amino acid such as disodium N-(carbo-p-tert. octaylphenoxypentaethoxy} glutamate as described in Knox and Wilson U.S. patent application Serial No. 600,679, filed July 30, 1956; or a sulfosuccinamate such as tetrasodiurn N-(1,2-dicarboxyethyl)-N-octadecy1 sulfosuccinamate or N-lauryl disodium sulfosuccinamate as described in Knox and Stenberg U.S. patent application Serial No. 691,125, filed October 21, 1957.

The addenda which we have described -rnay be used in various grinds of photographic emulsions. In addition to being useful in X-ray and other nonoptically sensitized emulsions they may also be used in orthochromatic, panchromatic, and infrared sensitive emulsions. They may be added to the emulsion before or after any sensitizing dyes which are used. Various silver salts may be used as the sensitive salt such as silver bromide, silver iodide, silver chloride, or mixed silver halides such as silver chlorobromide or silver bromoiodide. The agents may be used in emulsions intended for color photography, for example, emulsions containing color-forming couplers or emulsions to be developed by solutions containing couplers or other color-generating materials, emulsions of the mixed-packet type, such as described in Godowsky U.S. Patent 2,698,794, issued January 4, 1955, or emulsions of the mixed-grain type, such as described in Carroll and Hanson U.S. Patent 2,592,243, issued April 8, 1952. These agents can also be used in emulsions which form latent images predominantly on the surface of the silver halide crystal or in emulsions which form latent images predominantly inside the silver halide crystal, such as those described in Davey and Knott U.S. Patent 2,592,250, issued April 8, 1952.

They may also'be used in emulsions intended for use in diffusion transfer processes which utilize the undeveloped silver halide in the nonimage areas of the negative to form a positive by dissolving the undeveloped silver halide and precipitating it on a receiving layer in close proximitiy to the original silver halide emulsion layer. Such processes are described in Rott U.S. Patent 2,352,014, issued June 20, 1944, and Land U.S. Patents 2,584,029, issued January 29, 1952; 2,698,236, issued December 28, 1954; and 2,543,181, issued February 27, 1951; and Yackel et al. U.S. patent application Serial No. 586,705, filed May 23, 1956. They may also be used in color transfer processes which utilize the diifusion transfer of an imagewise distribution of developer, coupler or dye, from a light-sensitive layer to a second layer, while the two layers are in close proximity to one another. Color processes of this type are described in Land U.S. Patents 2,559,643, issued July 10, 1951, and 2,698,798, issued January 4, 1955; Land and Rogers Belgian Patents 554,933 and 554,934, granted August 12, 1957; International Polaroid Belgian Patents 554,212, granted July 16, 1957, and 554,935, granted August 12, 1957; Yutzy U.S. Patent 2,756,142, issued July 24, 1956 and Whitmore and Mader V U.S. patent application Serial No. 734,141, filed May 9, 1958.

In the preparation of the silver halide dispersions employed for preparing silver halide emulsions, there may i be employed as the dispersing agent for the silver halide in its preparation, gelatin or some other colloidal material such as colloidal albumin, a cellulose derivative, or a synthetic resin, for instance, a polyvinyl compound. Some colloids which may be used are polyvinyl alcohol or a hydrolyzed polyvinyl acetate as described in Lowe U.S. Patent 2,286,215, issued June 16, 1942; a far hydrolyzed cellulose ester such as cellulose acetate hydrolyzed to an acetyl content of 1926% as described in U.S. Patent 2,327,808 of Lowe and Clark, issued August 24, 1943; a water-soluble ethanolamine cellulose acetate as described in Yutzy U.S. Patent 2,322,085, issued June 15, 1943; :1 polyacrylamide having a combined acrylamide content of 3060% and a specific viscosity of 025-15 on an imidized polyacrylamide of like acrylamide content and viscosity as described in Lowe, Minsk and Kenyon U.S. Patent 2,541,474, issued February 13, 1951; zein as described in Lowe US. Patent 2,563,791, issued August 7, 1951; a vinyl alcohol polymer containing urethane carboxylic acid groups of the type described in Unruh and Smith US. Patent 2,768,154, issued October 23, 1956; or containing cyano-acetyl groups such as the vinyl alcoholvinyl cyanoacetate copolymer as described in Unruh, Smith and Priest US. Patent 2,808,331, issued October 1, 1957; or a polymeric material which results from polymerizing a protein or a saturated acylated protein with a monomer having a vinyl group as described in US. Patent 2,852,382 of lllingsworth, Dann and Gates, issued September 16, 1958.

If desired, compatible mixtures of two or more of these colloids may be employed for dispersing the silver halide in its preparation. Combinations of these antifoggants, sensitizers, hardeners, etc., may be used.

The sensitizing compounds of our invention can be used both in emulsions intended for bl-ack-and-white photography, or emulsions intended for color photography. When used for this latter purpose, they can be used in emulsions containing color-forming compounds or couplers, or they can be used in emulsions which are to be color-developed in developers containing the colorforming compounds or couplers. In either type of color photography, the particular color-forming compounds or couplers react with the oxidation products of color developers (particularly phenylenediamine developers) to provide subtractively-colored images. The colorforming compounds can be of the customary types employed in color photography, such as pyrazolone couplers for formation of the magenta image, phenolic couple-rs for formation of the cyan image and open-chain compounds containing a reactive methylene group for formation of the yellow image. Such couplers can be of the type which can be dispersed in a high-boiling, crystalloidal compound, which can be used as a vehicle for incorporating the color-forming compound in the photographic emulsion, or such couplers can be of the fat-tail varieties (see, for example, F.I.A.T., Final Report, No. 721 for examples thereof) which can be dispersed in the photographic silver halide emulsions. Both of these types of couplers are characterized by non-difiusing properties from the particular silver halide emulsions in which they are incorporated. The couplers or color-forming compounds can be incorporated in the silver halide emulsions by any of the common methods known to those skilled in the art.

Typical color-forming compounds or couplers which are useful in color photography, according to our invention, include the following:

Couplers producing cyan images -(p-amylphenoxybenzenesulfonamino) -1-naphthol 5- (N-benzyl-N-naphthalenesulfonamino l-naphthol S-(n-benzyl-N-n-valerylamino)-l-naphthol S-capr-oylamino-l-naphthol 2-ch1o-ro-5 N-n-valeryl-N-p-isopropylb enzylarnino -1- naphthol 2,4-dichloro-5- (p-nitrobenzoyl-B-o-hydroxyethylamino l-naphthol 2,4-dichloro-5-palmitylaminc-l-naphthol 2,2'-dihydroXy-5,5'-dibromostilbene 5-diphenylethersulfonamido l-naphthol l-hydroxy-2-(N-isoamyl-N-phenyl)naphthamide l-hydroxy-Z-(N-p-sec. amylphenyl)naphtharnide S-hydroxy-1-a-naphthoyl-1,2,3,4-tetrahydroquinoline 2-lauryl-4-chlorophenol 1-naphtho1-2-carboxylic-a-naphthalide 1-naphthol-S-sulfo-cyclohexylamide S-phenoxyacetamino-l-naphthol 5-;3-phenylpropionylamino-l-naphthol Monochlor-S- (N-'y-phenylpropyl-N-p-sec.-amylb enzoylamino)-l-naphthol 2-acetylamino-S-methylphenol 2-benzoylamino-3,S-dimethylphenol 2-u(p-tert. amylphenoxy) -n-butyrylamino-5-methylphenol 6-{'y{4- ['y-(2,4-di-tert. amylphenoxy)butyramido] phenoxy} acetamido} -2,4-dichloro-3-methylphenol l-hydroxy-Z- [6-(2,4-di tert. amylphenoxy) -n-butyl] naphthamide 2-a (p-tert. amylphenoxy) -n-butyrylamino-4-chloro-5- methylphenol 2-(p'-tert. amylphenoxy-p-benzoyl)amino-4-chloro-5- methylphenol 2- (4"-tert. amyl-3 '-phenoxybenzoylamino -3,5-dimethyll-phenol Z-phenylacetylamirro-4-chloro-5-methylphenol 2-benzoylamino-4-chloro-S-methylphenol 2-anilinoacetylamino-4-chloro-S-methylphenol 2-{4- [oc(4"t61"t. amylphenoxy)-n-butyrylamino] benzoylamino}-4-chloro-5-methylphenol 2- [4,3 (4"'-tert. amylphenoxy) benzoylarnino] benzoylamino-4-chloro-S-methylphenol 2-p-nitro-benzoylamino-4-ch1oro-5-methylphenol Z-m-aminobenzoyl-4-chloro-S-methylphenol 2-acetamino-4-chloro-5-methylphenol 2(4'-sec. amylbenzamino) -4-chloro-5-methylphenol 2 (4'-n-amyloxybenzamino -4-chloro-5-methylphenol 2 4'-phenoxybenzoylarnino phenol 2( 4"-tert. amyl-3 '-phenoxybenzoylamino) phenol 2- a-(4-tert. butylphenoxy) propionylamino] phenol 2- [oz- (4-tert. amyl phenoxypropionylamino] phenol 2- [N-methyl-N- 4"-tert. amyl-3 '-phenoxybenzoylamino) phenol 2-(4"-tert. amyl-3-phenoxybenzoylamino) -3-methyl-1- phenol 2-(4"-tert. amyl-3'-phenoxybenzoylamino) -6-methyl-1- phenol 2-(4-tert. amyl-3'-phenoxybenzoylamino)-3,6-dimethyl phenol 2,6-di(4"-tert. amyl-3-phenoxybenzoylamino) l-phenol 2-oz-(4'418ft. amylphenoxy) butyrylamino-l-phenol 2 4' '-tert. amyl-3 -phenoxybenzoylamino) -3 ,5 -dimethyll-phenol 2- [tx-(4'-tert. amylphenoxy) -n-butyrylamino] -5-methyll-phenol 2 (4-tert. amyl-3-phenoxybenzoylamino)-4-chloro-1- phenol 3 [cc- (4"-tert. amylphenoxy) -n-butyrylamino] -6-chlorophenol 3-(4"-tert. amyl-3-phenoxybenzoylamino phenol 2- [oc-(4'4Ie1t. amylphenoxy) -n-butyrylamino] -6-chlorophenol 3- x- 4'-tert. amylphen0xy) -n-butyrylamino] -4-chlorophenol 3- [oc-(4'-t61't. amylphenoxy) -n-butyrylamino] -5-chlorophenol t 3- OL- 4-tert. amylphenoxy) -n-butyrylam-ino] -2-chlorophenol 2-a-(4'-tert. amylphenoxybutyrylamino) -5-chlorophenol 2-(4"-tert. amyl-3'-phenoxybenzoylamino) -3-chlorophenol 5-benzene sulfonamino-l-naphthol 2,4-dichl0ro-5-benzenesulfonarnino-1-naphthol 2,4-dichloro-5-(p-toluenesulfonamino)-1-naphthol 5- 11123,4-tetrahydronaphthalene-6-sulfamino)-1-naph- 2,4-dichlo ro-5- 4bromodiphenyl-4-sulfon amino) -1-naphthol 5- quinoline-S-sulfamino) -1-naphtho1 8, 1947, can be used as couplers for the cyan image, e.g.

NHOO-oH-OQ-cum (EH5 or NEoo-cnotnn l or $2115 mrco-on-o-Qoun etc.

Couplers producing magenta images l-p-sec. amylphenyl-B-n-amyl-S-pyrazolone Z-cyarroacetyl-S-(p-sec. amylbenzoylamino) coum arone Z-cyanoacetylcoumarone-S- (n-amyl-p-sec. amylsulfanilide) Z-cyanoacetylcoumarone-S-(N-n-amyl-p-tert. amylsulfanilide) Z-cyanoacetylcoumarone-S sulfon-N-n-butylanilide 2-cyanoacetyl-5-benzoylamino-coumarone 2-cyanoacetylcoumarone-S-sulfondimethylamide Z-cyanoacetylcoumarone--sulfon-N-methylanilide 2-cyanoacetylnaphthalene sulfon-N-methylanilide 2-cyanoacetylcoumarone-5-(N-y-phenylpropyl) -p-ter-t.

amylsulfonanilide l-p-laurylphenyh3-methyl-5-pyrazolone 1-fl-naphthyl-3-amyl-5-pyrazolone 1sp-nitrephenyl itmamyl-S-pyrazolone 1p-phenoxyphenyl-3-n-amyl-S-pyrazolone 1-phenyl-3-n-amyla5apyrazolone 1,4-phenylene bis-3-( l-phenyl-S-pyrazolone) 1-phenyl-3-aeetylamino-S-pyrazolone 1-phenyl-3-propionylamino-S-pyrazolone 1-phenyl-3 -n -valerylamino-S-pyrazolone 1-phenyl-3 -chloroacetylamino5-pyrazolone l-phenyl-3-dichloroacetylaminod-pyrazolone l-pheny1-3-benzoylamino-5-pyrazolone 1-phenyl-3-(m-aminobenzoyl) amino-S-pyrazolone 1-phenyl-3-(p-sec. amylbenzoylarnino -5-pyrazolone 1-phenyl-3-diamylbenzoylamino-i-pyrazolone 1-phenyl-3-B-naphthoylamino-S-pyrazolone 1-phenyl-3-phenylcarbamylamino-S-pyrazolone 1-phenyl-3paImityIaminod-pyrazolone I l-plienyl-3-benzenesulfonylaminod-pyrazolone 1- (p-phenoxyphenyl -3- (.p-tert. .amyloxybenzoyl) amino- 5 -pyr azolone 1-(2.,4', 6,'-tribromophenyl )-3-benzamido-5-pyrazolone l-( 2',4',6'-trichlorophenyl) -3-benzamido5-pyrazolone 1-(2f ,A,6,'-t1'ichlorophenyl)-3-phenylacetamido-5 -pyrazolone. 1-( 2',4,6"-'tribromophenyl) -3 -phenylacetamido-5-pyrazolone 1( 2',4-dichlor ophenyl ),-3 [3"-(2"',4"'-di-tert. amylphenoxyacetamido.) benz amido] -5-pyrazolone 1-(2',4',6'-trichlorophenyl) -3- [3"-( 2"',4"-di-tert.' amylphenoxyacet-amido benzamido] -5-pyrazolo ne 1-(2f,4,6-tribromophenyl)-3.- [3"-(2",4"'-ditert. amylphenoxyacetamido) benzamido] -5-pyrazolone l-( 2,4',6'-trichlorophenyl-) 3- [[3- (2"", 4"-di tert. amylphenoxy) -propionamido] -5-pyraz olone 1-(2',4',6'-tribromophenyl) -3- [fi-( 2"',4-di-tert. amylphenoxy)-propionamido]-5 pyrazo1one 1-("2"',5-'-dichloro) -3- [3'- (4""tert. emylphenoxy benza mido] -5-pyrazolone 1- 2',4',6-tribromophenyl) -3- 3"- (4'-tert. amylphenoxy) -benzamido] -5-pyrazolone- 1-( Z',5'-dichlorophenyl) -3- [3"-(2"',4'-di-tert. amylphenoxyacetamido) benzamido] -5-pyrazolone Couplers producing yellow images N amyl-p-benzoyl acetaminobenzenesulfonate N- 4-anisoylacetaminob enzenesulfon-yl) -N-b enzyl-m-toluidine N- 4-b enzoylacetaminobenzenesulfonyl) -N-benzyl-m-.to-

luidine N- (4-benzoyl acetamionbenzenesulfonyl -N-n-amyl-p-tojluidine N- 4-benzoylacetaminob enzenesulfonyl) -N-benzylaniline w- (p-B enzoylbenzoyl) acetanilide w-B enzoylacet-2,S -dichloroanilide w-Benzoyl-p-sec. amylacetanilide N,N-di w-benzoylacetyl) -p-phenylenediamine N,N'diaceto acetamino diphenyl Ot-{3- [a- (2,4-di-tert.-amylphenoxy) butyramido] benzoyl}- Z-m ethoxyacetanilide a-{S- m-(2,4-di-tert.-amylphenoxy)acetamido benzoyl}- 2-methoxyacetanilide 4,4'-di- (acetoacetamino) -3,3-dirnethyldiphenyl p,p'-di- (aceto acetamino diphenylrnethane Ethyl-p-benzoylacetaminobenzenesulfonate N0nyl-p-benzoylacetaminobenzenesulfonate N-phenyl-N'- (p-acetoacetaminophenyl) urea n-Propyl-p-benzoylacetaminobenzenesulfonate acetoacetpiperidine w-Benzoylacetpiperidide N(w-beuzoylacety1)-1,2,3 ,4-tetrahydroquinoline N (w-benzoyl acetyl )morpholine The above color-forming compounds produce colored images upon development of the exposed emulsions with color developers, such as the phenylenediamine color developers. Especially useful color developers are those derived from p-phenylenediamines containing at least one primary amino group, such as N,N-dimethyl-p-phenylenediamine, N,N-diethyl-p-phenylenediamine, N-carbamidomethyl N -methyl p-phenylenediamine, N -carbamidomethyl N tetrahydrofurfuryl 2 methyl-p-phenylenediarnine, N -ethyl-N -carboxymethyl-2 methyl-p-phenylenediamine, N -carbamidomethyl-N -ethyl 2 methyl-pphenylenediamine, N ethyl N tetrahydrofurfuryl 2- methyl-p-aminophenol, 3-acetylamino-4-aminodirnethylaniline, N ethyl-N-fl-methanesulfonamidoethyl-4-aminoaniline, N-ethyl-N-fi-methanesulfonamidoethyl-Bmethyl- 4-aminoaniline, the sodium salt of N-methyl-N-fi-sulfoethyl-p-phenylenediamine, etc.

As can be seen by reference to the large number of sensitizers included within our invention, as well as the large number of color-forming compounds which can be employed in combination therewith, a number of combinations of sensitizing compounds and color-forming compounds is possible. In order to determine quickly the effectiveness of a particular combination, it has been found that the screening technique described by Pontius and Thompson in Photo. Sci. Eng, vol. 1, pages 4-51, can be used to get an idea of the potential effectiveness of a given combination for use in a photographic color element containing a coupler. This technique does not necessitate the preparation of any coupler dispersions, but the sensitizers can be added to ordinary photographic silver halide emulsions of the type used in black-and-white photography, such as gelatino-silver-bromiodide emulsions, and the emulsions exposed in an intensity scale scnsitorneter to daylight quality radiation for a fraction of a second (usually 1/25) and processed for about 15 minutes in a phenylenediamine color developer, to which has been added 10 g. per liter of H-acid. The pH of this developer is usually adjusted to 10.8 by adding so dium hydroxide. A suitable developer composition for 13 H-acid (1 amino 8 naphtho1-3,6-disulfonic acid g 10.0 4-amino-3-methyl-N-ethyl N-(p methyl sulfonamidoethyl aniline sulfate g 8.0 Sodium carbonate monohydrate g 40.0 Sodium bromide g 1.5 Sodium thiocyanpteg 0.2 Benzotriazole g .03

Water total to 1 liter, pH 10.811.

The relative speed, gamma and fog for coatings processed in this manner are given in Table I below.

The following technique was used to determine the efiectiveness of our compounds as sensitizers in photograhic silver halide emulsions designed for black-andwhite photography.

An ordinary photographic silver bromiodide emulsion containing a sensitizing dye, a sulfur sensitizer of the type mentioned in Sheppard U.S. Patent 1,623,499, mentioned above, and gold sensitized in the manner indicated in U.S. Patent 2,448,060, mentioned above, was divided into several portions. Sensitizing compounds obtained as described above and identified by the numbers given above, were then added in solutions in an organic solvent, such as ethanol or N,N-dimethylformamide in the amounts indicated in Table I below. The various portions of emulsions were then coated on transparent supports, such as cellulose acetate, and then dried. The dried coatings were exposed for about 1 /25 sec. to daylight quality radiation in Eastman Type lb Sensitometer. The coatings were then developed for about 5 minutes in a photographic developer having the following composition:

G. N-methyl-p-aminophenol sulfate 2.5 Hydroquinone 2.5 Sodium sulfite (dry) 30.0 Sodium borare 10.0 Potassium bromide 0.5

TABLE I 5 DK-50 15 color developer Com- .G./ml. pound silver N o. halide Relative Gamma Fog Relative Gamma Fog speed speed The eifect of our polythiaalkylenedioi sensitizers has been illustrated above with particular reference to-ordinary photographic silver bromide emulsions, although it is to be understood that other silver halide emulsions can be employed to like advantage.

While the prior art has previously suggested adding various thioether compounds to photographic silver halide emulsions for the purpose of increasing sensitivity, this has been done usually in compounds containing an ionic substituent on the terminal positions. However, it has been found that the compounds useful in our invention have marked advantages .over such types of sensitizers. The data in the following table were obtained in exactly the manner described above for the coatings of Table I, and it will be recognized that these data clearly establish the superiority of the present. non-ionic 14 compounds over the ionic counterparts suggested in the prior art.

TABLE II 5 minutes DK-EO 'Coat- Coning Description centra- N 0. tion Speed Gamma Fog g lmole (2)-.-. Oontrol 1. 53 16 (b) 7,10,13-trithianonadeeaue-bis- 03 97 1. 36 17 (pyridinium perchlorate). (0).... do .15 100 1.30 .24 (d do .75 79 1.08 .32 (e). 7,13-dithianonadecane-1,19-bis- O3 102 1. 64 15 (pyridinium p toluenesuluate). (f) 76 1. 38 34 (g) 100 1. 26 13 (h) 141 1. 38 14 (1)..... Control 100 1.29 14 (j) 7,13-dithia-1,19-n0nadecandiol 3 148 1. 18 21 It has also been found that while tetraethylene glycol is of no practical use in increasing the sensitivity of photographic silver halide emulsions, the corresponding compounds of our invention are quite useful in sensitiz ing photographic silver halide emulsions in the manner described.

The following data show the effect produced by adding a sensitizing compound of our invention to an ordinary negative speed silver bromiodide emulsion which had been digested to optimum sensitivity with a mixture of a labile sulfur compound of the type shown in U.S. Patent 1,623,499 and a gold compound of the type shown in U.S. Patent 2,448,060. The emulsion had been red-sensitized to that region of the spectrum lying between about 600 and 700 my and it contained a conpler dispersion of one of the color-forming compounds for producing the cyan image upon color development, such as a dispersion ofaphenol coupler, e.g., any one of Couplers Nos. 1 to, 6 of Fierke U.S. Patent 2,801,171 (column 2) in a suitable solvent, such as tri-o-cresylphosphate or dibutylphthalate. In aliquot samples of the same emulsions, there were incorporated polythiaalkylenediol sensitizers as identified in the table. The emulsions were then coated on conventional film support and dried. The coatings were exposed in an Eastman Type Ib Sensitometer for 1/50 sec. to the light emitted by a SOD-watt tungsten lamp adjusted to 6100 K. and further modulated by a Wratten No. 15 Filter. The exposed coatings were then processed through a reversal process, such as the following:

0.1% solution of potassium iodide cc 10.0 Water to make 1 liter.

The element was then thoroughly washed with water and treated in a hardening bath having the following composition:

Potassium chrome alum crystals Water to make 1 liter. f

The element was then thoroughly washed with water and treated for 30 seconds in a solution having the following composition:

Sodium borohydride 0.25 Sodium hydroxide Water to make 1 liter.

The element was then treated in a color. developer having the following composition:

Water to make 1 liter.

4: amino N ethyl N 8 methanesulfonamidoethyl)- m-toluldine sesquisulfate monohydrate.

The element was then thoroughly washed with water and treated in a clearing and fixing bath having the fol lowing composition:

Sodium thiosulfate .g 150.0 sodium bisulfite g 20.0 Water to make 1 liter.

The element was then treated in a bleach bath having the following composition:

Potassium dichromate g 5.0 Potassium ferricyanide g 70.0 Potassium bromide g 20.0

Water to make 1 liter.

The element was again washed and treated once again with the clearing and fixing bathidentified above. The element was again Washed and treated in a stabilizing bath having the following composition:

Formaldehyde 37% by weight); c 7.0 Dispersing agent* g 0.5 Water to make 1 liter.

Such as TritnX 100, i.e., an ulky'laryl polyether alcohol (octylphenoxypolyethoxyethanol).

The following photographic data were obtained:

TABLE III Goat Con- Relatng Description centra- A Dmnx. tive No. tion speed gJrnole Ref. 160 1 -l.00 209 2 l.24 225. 1 -.55 191 2 .66' 234 While the effect of our sensitizers has been illustrated in Table III above with respect to a photographic element having only one color-sensitized layer, it is to be understood that the advantages are also obtained in multilayer films containing a plurality of photographic emulsion layers which have their sensitivity in different regions of the spectrum. The sensitizers are effective not only-in red-sensitized emulsions but in emulsions whichhave their maximum sensitivity in the blue region of the spectrum, or inemulsions which have their maximum sensitivity in the green region of the spectrum.

The invention has been described in detail with particular reference to preferred embodiments thereof, but it will be understood that variations and. modifications can be effected within the spirit and scope of the invention as described hereinabove and as defined in the appended claims- What we claim as our invention and desire secured by Letters Patent of the United States is:

1. A photographic silver halide emulsion sensitized with a non-polymeric sensitizer selected from the class represented by the following general formula:

7 HOR (-SR --S'-ROH wherein R and R each represents a hydrocarbon alkylene 15 group containing from about 2 to 10 carbon atoms and d represents a positive integer of from 1 to 3.

2. A photographic silver halide emulsion containing a sensitizing amount of a compound selected from the class represented by the following general formula:

wherein m and it each represents a positive integer of from about 2 to 10.

3. A photographic silver halide developing-out emulsion sensitized with a gold compound and a labile sulfur compound and containing a sensitizing amount of a nonpolymeric compound selected from those represented by the following general formula:

wherein R and R each represents a hydrocarbon alkylene group containing from about 2 to 10 carbon atoms and d represents a positive integer of from about 1 to 3.

4. A photographic silver halide developing-out emulsion sensitized with a gold compound and a labile sulfur compound and containing a sensitizing amount of a nonpolymeric compound selected from those represented by the following general formula:

wherein m and n each represents a positive integer of from about 2 to 10.

5. A photographic silver halide emulsion containing a sensitizing amount of the compound represented by the following formula:

HO(CH S(CH S(CH 0H 6. A photographic silver halide emulsion containing a sensitizing amount of the compound represented by the following formula:

H 2) 6 2)'s 2) 60H 7. A photographic silver halide emulsion containing a sensitizing amount of the compound represented by the following formula:

HO (CH S(CH S(CH 0H 8. A photographic silver halide emulsion containing a sensitizing amount of the compound represented by the following formula:

HO (CH S (CH S (CH 0H 9. A photographic silver halide emulsion containing a sensitizing amount of the compound represented by the following formula:

10. A photographic silver halide emulsion containing a color-forming compound capable of coupling with the oxidation products of a color developer containing at least one primary aminoaryl group to produce a colored compound, said emulsion containing a sensitizing amount of a compound selected from those represented by the following general formula:

represents a positive integer of from about 1 to 3.

11. A photographic silver halide emulsion containing a color-forming compound capable of coupling with the oxidation products of a color developer containing at least one primary aminoaryl group to produce a colored compound, said emulsion containing a sensitizingamount of a compound selected from those represented by the following general formula:

wherein m and n each represents a positive integer of from about 2 to 10.

12. A photographic silver halide emulsion containing a color-forming compound capable of coupling with the oxidation products of a color developer containing at least one primary aminoaryl group to produce a colored compound, said emulsion being sensitized with a gold compound, and a labile sulfur compound and containing a sensitizing amount of a compound selected from those represented by the following general formula:

HO-(CH S-(CH S-(CH -OH wherein m and 12 each represents a positive integer of from about 2 to 10.

14. A photographic silver halide emulsion containing a color-forming compound capable of coupling with the oxidation products of a color developer containing at least one primary aminoaryl group to produce a colored compound, said emulsion containing a sensitizing amount of the compound represented by the following formula:

15. A photographic silver halide emulsion containing a color-forming compound capable of coupling with the 18 oxidation products of a color developer containing at least one primary aminoaryl group to produce a colored compound, said emulsion containing a sensitizing amount of the compound represented by the following formula:

16. A photographic silver halide emulsion containing a color-forming compound capable of coupling with the oxidation products of a color developer containing at least one primary aminoaryl group to produce a colored compound, said emulsion containing a sensitizing amount of the compound represented by the following formula:

17. A photographic silver halide emulsion containing a color-forming compound capable of coupling with the oxidation products of a color developer containing at least one primary aminoaryl group to produce a colored compound, said emulsion containing a sensitizing amount of p the compound represented by the following formula:

HO(CH S(CH S(CH OH 18. A photographic silver halide emulsion containing a color-forming compound capable of coupling with the oxidation products of a color developer containing at least one primary aminoaryl group to produce a colored compound, said emulsion containing a sensitizing amount of the compound represented by the following formula:

References Cited in the file of this patent UNITED STATES PATENTS Moessen July 31, 1956 Chechak et al Aug. 19, 1958 

1. A PHOTOGRAPHIC SILVER HALIDE EMULSION SENSITIZED WITH A NON-POLYMERIC SENSITIZER SELECTED FROM THE CLASS REPRESENTED BY THE FOLLOWING GENREAL FORMULA: 